Wearable cardioverter defibrillator (WCD) system reacting to high-frequency ECG noise

ABSTRACT

In embodiments a wearable cardioverter defibrillator (WCD) system is worn by an ambulatory patient. The WCD system analyzes an ECG signal of the patient, to determine whether or not the patient should be given an electric shock to restart their heart. If the WCD system determines that such a shock should be given, then it also determines whether or not a High Frequency (H-F) noise criterion is met by the ECG signal. If that H-F noise criterion is not met, the patient can be shocked. If, however, that H-F noise criterion is met, then the WCD system can confirm before shocking, by sensing another portion of the ECG signal, analyzing again, and so on. Thanks to the confirmation before shocking, the possibility is diminished that the ECG signal will indicate that a shock is needed falsely, due to H-F noise. This can further reduce false patient alarms, and so on.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority from U.S. Provisional PatentApplication Ser. No. 62/538,159, filed on Jul. 28, 2017.

BACKGROUND

When people suffer from some types of heart arrhythmias, the result maybe that blood flow to various parts of the body is reduced. Somearrhythmias may even result in a Sudden Cardiac Arrest (SCA). SCA canlead to death very quickly, e.g. within 10 minutes, unless treated inthe interim.

Some people have an increased risk of SCA. People at a higher riskinclude patients who have had a heart attack, or a prior SCA episode. Afrequent recommendation is for these people to receive an ImplantableCardioverter Defibrillator (ICD). The ICD is surgically implanted in thechest, and continuously monitors the patient's electrocardiogram (ECG).If certain types of heart arrhythmias are detected, then the ICDdelivers an electric shock through the heart.

After being identified as having an increased risk of an SCA, and beforereceiving an ICD, these people are sometimes given a WearableCardioverter Defibrillator (WCD) system. (Early versions of such systemswere called wearable cardiac defibrillator systems.) A WCD systemtypically includes a harness, vest, or other garment that the patient isto wear. The WCD system further includes electronic components, such asa defibrillator and electrodes, coupled to the harness, vest, or othergarment. When the patient wears the WCD system, the external electrodesmay then make good electrical contact with the patient's skin, andtherefore can help sense the patient's ECG. If a shockable heartarrhythmia is detected, then the defibrillator delivers the appropriateelectric shock through the patient's body, and thus through the heart.

Often the patient's ECG includes electrical noise, which can be createdat the interface of the electrodes with the patient's skin. Such noisecan make it difficult to diagnose the patient's condition accuratelyfrom the ECG, and detect whether or not the patient is having ashockable arrhythmia.

All subject matter discussed in this Background section of this documentis not necessarily prior art, and may not be presumed to be prior artsimply because it is presented in this Background section. Plus, anyreference to any prior art in this description is not, and should not betaken as, an acknowledgement or any form of suggestion that such priorart forms parts of the common general knowledge in any art in anycountry. Along these lines, any recognition of problems in the prior artdiscussed in this Background section or associated with such subjectmatter should not be treated as prior art, unless expressly stated to beprior art. Rather, the discussion of any subject matter in thisBackground section should be treated as part of the approach takentowards the particular problem by the inventors. This approach in and ofitself may also be inventive.

BRIEF SUMMARY

The present description gives instances of wearable cardioverterdefibrillator (WCD) systems, storage media that may store programs, andmethods, the use of which may help overcome problems and limitations ofthe prior art.

In embodiments a WCD system is worn and/or carried by an ambulatorypatient. The WCD system analyzes an ECG signal of the patient, todetermine whether or not the patient should be given an electric shockto restart their heart. If the WCD system determines that such a shockshould be given, then it also determines whether or not a High Frequency(H-F) noise criterion is met by the ECG signal. If that H-F noisecriterion is not met, the patient can be shocked. If, however, that H-Fnoise criterion is met, then the WCD system can confirm before shocking,by sensing another portion of the ECG signal, analyzing again, and soon.

An advantage of embodiments is that, thanks to the confirmation beforeshocking, the possibility is diminished that the ECG signal willindicate that a shock is needed falsely, due to H-F noise. Furthermore,since the patient is alerted by an alarm before shocking, the incidenceof false alarms can be diminished, and the patient may be more compliantin actually wearing and/or carrying the WCD system.

These and other features and advantages of the claimed invention willbecome more readily apparent in view of the embodiments described andillustrated in this specification, namely in this written specificationand the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of components of a sample wearable cardioverterdefibrillator (WCD) system, made according to embodiments.

FIG. 2 is a diagram showing sample components of an externaldefibrillator, such as the one belonging in the system of FIG. 1, andwhich is made according to embodiments.

FIG. 3A is a diagram of selected components for illustrating how an ECGsignal sensed by a pair of electrodes may be processed according toembodiments to yield a heart rate and other information.

FIG. 3B is a conceptual diagram for illustrating examples of how a firstECG signal may be used for a heart rate computation even if it includesnoise events, while a second ECG signal may be used for performing ananalysis and/or confirming a shock decision according to embodiments.

FIG. 4 is a conceptual diagram for illustrating sample possibledeterminations made about the patient from portions of the patient's ECGsignal according to embodiments.

FIG. 5 is a conceptual diagram for illustrating other sample possibledeterminations made about the patient from portions of the patient's ECGsignal according to additional embodiments.

FIG. 6 is a flowchart for illustrating sample methods according toembodiments.

FIG. 7 shows sample time diagrams for illustrating an example of how apatient's ECG signal may be segmented and for how a patient's heart ratemay be computed according to embodiments.

FIG. 8 shows sample time diagrams for illustrating how a patient'sdetected ECG signal may be segmented for detecting noise eventsaccording to embodiments.

FIG. 9 shows sample time diagrams for illustrating possibledeterminations about whether or not a segment noise criterion is met inindividual ECG segments according to embodiments.

FIG. 10 shows sample time diagrams for illustrating other possibledeterminations about whether or not a segment noise criterion is met inindividual ECG segments according to embodiments.

DETAILED DESCRIPTION

As has been mentioned, the present description is about wearablecardioverter defibrillator (WCD) systems, media that store instructions,and methods. Embodiments are now described in more detail.

A wearable cardioverter defibrillator (WCD) system made according toembodiments has a number of components. These components can be providedseparately as modules that can be interconnected, or can be combinedwith other components, etc.

FIG. 1 depicts a patient 82. Patient 82 may also be referred to as aperson and/or wearer, since the patient is wearing components of the WCDsystem. Patient 82 is ambulatory, which means patient 82 can walkaround, and is not necessarily bed-ridden.

FIG. 1 also depicts components of a WCD system made according toembodiments. One such component is a support structure 170 that iswearable by patient 82. It will be understood that support structure 170is shown only generically in FIG. 1, and in fact partly conceptually.FIG. 1 is provided merely to illustrate concepts about support structure170, and is not to be construed as limiting how support structure 170 isimplemented, or how it is worn.

Support structure 170 can be implemented in many different ways. Forexample, it can be implemented in a single component or a combination ofmultiple components. In embodiments, support structure 170 could includea vest, a half-vest, a garment, etc. In such embodiments such items canbe worn similarly to parallel articles of clothing. In embodiments,support structure 170 could include a harness, one or more belts orstraps, etc. In such embodiments, such items can be worn by the patientaround the torso, hips, over the shoulder, etc. In embodiments, supportstructure 170 can include a container or housing, which can even bewaterproof. In such embodiments, the support structure can be worn bybeing attached to the patient by adhesive material, for example as shownin U.S. Pat. No. 8,024,037. Support structure 170 can even beimplemented as described for the support structure of US Pat. App. No.US2017/0056682, which is incorporated herein by reference. Of course, insuch embodiments, the person skilled in the art will recognize thatadditional components of the WCD system can be in the housing of asupport structure instead of being attached externally to the supportstructure, for example as described in the US2017/0056682 document.There can be other examples.

A WCD system according to embodiments is configured to defibrillate apatient who is wearing it, by delivering an electrical charge to thepatient's body in the form of an electric shock delivered in one or morepulses. FIG. 1 shows a sample external defibrillator 100, and sampledefibrillation electrodes 104, 108, which are coupled to externaldefibrillator 100 via electrode leads 105. Defibrillator 100 anddefibrillation electrodes 104, 108 can be coupled to support structure170. As such, many of the components of defibrillator 100 could betherefore coupled to support structure 170. When defibrillationelectrodes 104, 108 make good electrical contact with the body ofpatient 82, defibrillator 100 can administer, via electrodes 104, 108, abrief, strong electric pulse 111 through the body. Pulse 111 is alsoknown as shock, defibrillation shock, therapy and therapy shock. Pulse111 is intended to go through and restart heart 85, in an effort to savethe life of patient 82. Pulse 111 can further include one or more pacingpulses, and so on.

A prior art defibrillator typically decides whether to defibrillate ornot based on an ECG signal of the patient. However, externaldefibrillator 100 may initiate defibrillation (or hold-offdefibrillation) based on a variety of inputs, with ECG merely being oneof them.

Accordingly, it will be appreciated that signals such as physiologicalsignals containing physiological data can be obtained from patient 82.While the patient may be considered also a “user” of the WCD system,this is not a requirement. That is, for example, a user of the wearablecardioverter defibrillator (WCD) may include a clinician such as adoctor, nurse, emergency medical technician (EMT) or other similarlysituated individual (or group of individuals). The particular context ofthese and other related terms within this description should beinterpreted accordingly.

The WCD system may optionally include an outside monitoring device 180.Device 180 is called an “outside” device because it could be provided asa standalone device, for example not within the housing of defibrillator100. Device 180 can be configured to sense or monitor at least one localparameter. A local parameter can be a parameter of patient 82, or aparameter of the WCD system, or a parameter of the environment, as willbe described later in this document. Device 180 may include one or moretransducers or sensors that are configured to render one or morephysiological inputs or signals from one or more patient parameters thatthey sense.

Optionally, device 180 is physically coupled to support structure 170.In addition, device 180 can be communicatively coupled with othercomponents, which are coupled to support structure 170. Suchcommunication can be implemented by a communication module, as will bedeemed applicable by a person skilled in the art in view of thisdescription.

FIG. 2 is a diagram showing components of an external defibrillator 200,made according to embodiments. These components can be, for example,included in external defibrillator 100 of FIG. 1. The components shownin FIG. 2 can be provided in a housing 201, which may also be referredto as casing 201.

External defibrillator 200 is intended for a patient who would bewearing it, such as patient 82 of FIG. 1. Defibrillator 200 may furtherinclude a user interface 280 for a user 282. User 282 can be patient 82,also known as wearer 82. Or, user 282 can be a local rescuer at thescene, such as a bystander who might offer assistance, or a trainedperson. Or, user 282 might be a remotely located trained caregiver incommunication with the WCD system.

User interface 280 can be made in a number of ways. User interface 280may include output devices, which can be visual, audible or tactile, forcommunicating to a user by outputting images, sounds or vibrations.Images, sounds, vibrations, and anything that can be perceived by user282 can also be called human-perceptible indications. There are manyexamples of output devices. For example, an output device can be alight, or a screen to display what is sensed, detected and/or measured,and provide visual feedback to rescuer 282 for their resuscitationattempts, and so on. Another output device can be a speaker, which canbe configured to issue voice prompts, beeps, loud alarm sounds and/orwords to warn bystanders, etc.

User interface 280 may further include input devices for receivinginputs from users. Such input devices may additionally include variouscontrols, such as pushbuttons, keyboards, touchscreens, one or moremicrophones, and so on. An input device can be a cancel switch, which issometimes called an “I am alive” switch or “live man” switch. In someembodiments, actuating the cancel switch can prevent the impendingdelivery of a shock.

Defibrillator 200 may include an internal monitoring device 281. Device281 is called an “internal” device because it is incorporated withinhousing 201. Monitoring device 281 can sense or monitor patientparameters such as patient physiological parameters, system parametersand/or environmental parameters, all of which can be called patientdata. In other words, internal monitoring device 281 can becomplementary or an alternative to outside monitoring device 180 ofFIG. 1. Allocating which of the parameters are to be monitored by whichof monitoring devices 180, 281 can be done according to designconsiderations. Device 281 may include one or more transducers orsensors that are configured to render one or more physiological inputsfrom one or more patient parameters that it senses.

Patient parameters may include patient physiological parameters. Patientphysiological parameters may include, for example and withoutlimitation, those physiological parameters that can be of any help indetecting by the wearable defibrillation system whether the patient isin need of a shock, plus optionally their medical history and/or eventhistory. Examples of such parameters include the patient's ECG, bloodoxygen level, blood flow, blood pressure, blood perfusion, pulsatilechange in light transmission or reflection properties of perfusedtissue, heart sounds, heart wall motion, breathing sounds and pulse.Accordingly, monitoring devices 180, 281 may include one or more sensorsconfigured to acquire patient physiological signals. Examples of suchsensors or transducers include electrodes to detect ECG data, aperfusion sensor, a pulse oximeter, a device for detecting blood flow(e.g. a Doppler device), a sensor for detecting blood pressure (e.g. acuff), an optical sensor, illumination detectors and sensors perhapsworking together with light sources for detecting color change intissue, a motion sensor, a device that can detect heart wall movement, asound sensor, a device with a microphone, an SpO₂ sensor, and so on. Inview of this disclosure, it will be appreciated that such sensors canhelp detect the patient's pulse, and can therefore also be called pulsedetection sensors, pulse sensors, and pulse rate sensors. Pulsedetection is also taught at least in Physio-Control's U.S. Pat. No.8,135,462, which is hereby incorporated by reference in its entirety. Inaddition, a person skilled in the art may implement other ways ofperforming pulse detection. In such cases, the transducer includes anappropriate sensor, and the physiological input is a measurement by thesensor of that patient parameter. For example, the appropriate sensorfor a heart sound may include a microphone, etc.

In some embodiments, the local parameter is a trend that can be detectedin a monitored physiological parameter of patient 282. A trend can bedetected by comparing values of parameters at different times.Parameters whose detected trends can particularly help a cardiacrehabilitation program include: a) cardiac function (e.g. ejectionfraction, stroke volume, cardiac output, etc.); b) heart ratevariability at rest or during exercise; c) heart rate profile duringexercise and measurement of activity vigor, such as from the profile ofan accelerometer signal and informed from adaptive rate pacemakertechnology; d) heart rate trending; e) perfusion, such as from SpO₂ orCO₂; f) respiratory function, respiratory rate, etc.; g) motion, levelof activity; and so on. Once a trend is detected, it can be storedand/or reported via a communication link, along perhaps with a warning.From the report, a physician monitoring the progress of patient 282 willknow about a condition that is either not improving or deteriorating.

Patient state parameters include recorded aspects of patient 282, suchas motion, posture, whether they have spoken recently plus maybe alsowhat they said, and so on, plus optionally the history of theseparameters. Or, one of these monitoring devices could include a locationsensor such as a Global Positioning System (GPS) location sensor. Such asensor can detect the location, plus a speed can be detected as a rateof change of location over time. Many motion detectors output a motionsignal that is indicative of the motion of the detector, and thus of thepatient's body. Patient state parameters can be very helpful innarrowing down the determination of whether SCA is indeed taking place.

A WCD system made according to embodiments may include a motiondetector. In embodiments, a motion detector can be implemented withinmonitoring device 180 or monitoring device 281. Such a motion detectorcan be made in many ways as is known in the art, for example by using anaccelerometer. In this example, a motion detector 287 is implementedwithin monitoring device 281.

A motion detector of a WCD system according to embodiments can beconfigured to detect a motion event. In response, the motion detectormay render or generate, from the detected motion event or motion, amotion detection input that can be received by a subsequent device orfunctionality. A motion event can be defined as is convenient, forexample a change in motion from a baseline motion or rest, etc. In suchcases, a sensed patient parameter is motion.

System parameters of a WCD system can include system identification,battery status, system date and time, reports of self-testing, recordsof data entered, records of episodes and intervention, and so on.

Environmental parameters can include ambient temperature and pressure.Moreover, a humidity sensor may provide information as to whether it islikely raining. Presumed patient location could also be considered anenvironmental parameter. The patient location could be presumed, ifmonitoring device 180 or 281 includes a GPS location sensor as per theabove, and if it is presumed that the patient is wearing the WCD system.

Defibrillator 200 typically includes a defibrillation port 210, such asa socket in housing 201. Defibrillation port 210 includes electricalnodes 214, 218. Leads of defibrillation electrodes 204, 208, such asleads 105 of FIG. 1, can be plugged into defibrillation port 210, so asto make electrical contact with nodes 214, 218, respectively. It is alsopossible that defibrillation electrodes 204, 208 are connectedcontinuously to defibrillation port 210, instead. Either way,defibrillation port 210 can be used for guiding, via electrodes, to thewearer the electrical charge that has been stored in an energy storagemodule 250 that is described more fully later in this document. Theelectric charge will be the shock for defibrillation, pacing, and so on.

Defibrillator 200 may optionally also have a sensor port 219 in housing201, which is also sometimes known as an ECG port. Sensor port 219 canbe adapted for plugging in sensing electrodes 209, which are also knownas ECG electrodes and ECG leads. It is also possible that sensingelectrodes 209 can be connected continuously to sensor port 219,instead. Sensing electrodes 209 are types of transducers that can helpsense an ECG signal, e.g. a 12-lead signal, or a signal from a differentnumber of leads, especially if they make good electrical contact withthe body of the patient and in particular with the skin of the patient.Sensing electrodes 209 can be attached to the inside of supportstructure 170 for making good electrical contact with the patient,similarly with defibrillation electrodes 204, 208.

Optionally a WCD system according to embodiments also includes a fluidthat it can deploy automatically between the electrodes and thepatient's skin. The fluid can be conductive, such as by including anelectrolyte, for establishing a better electrical contact between theelectrode and the skin. Electrically speaking, when the fluid isdeployed, the electrical impedance between the electrode and the skin isreduced. Mechanically speaking, the fluid may be in the form of alow-viscosity gel, so that it does not flow away from the electrode,after it has been deployed. The fluid can be used for bothdefibrillation electrodes 204, 208, and for sensing electrodes 209.

The fluid may be initially stored in a fluid reservoir, not shown inFIG. 2, which can be coupled to the support structure. In addition, aWCD system according to embodiments further includes a fluid deployingmechanism 274. Fluid deploying mechanism 274 can be configured to causeat least some of the fluid to be released from the reservoir, and bedeployed near one or both of the patient locations, to which theelectrodes are configured to be attached to the patient. In someembodiments, fluid deploying mechanism 274 is activated prior to theelectrical discharge responsive to receiving activation signal AS from aprocessor 230, which is described more fully later in this document.

The intent for a WCD system is to shock when needed, and not shock whennot needed. An ECG signal may provide sufficient data for making ashock/no shock determination. The problem is that, at any given point intime, some of these ECG signals may include noise, while others not. Thenoise may be due to patient movement, how well the electrodes contactthe skin, and so on. The inventor has identified that some types of ECGnoise for a WCD system can be classified as High-Frequency (H-F) noise,while other types of such ECG noise can be classified as High-Amplitude(H-A) noise. The noise problem for a WCD may be further exacerbated bythe desire to use dry, non-adhesive monitoring electrodes. Dry,non-adhesive electrodes are thought to be more comfortable for thepatient to wear in the long term, but may produce more noise than aconventional ECG monitoring electrode that includes adhesive to hold theelectrode in place and an electrolyte gel to reduce the impedance of theelectrode-skin interface.

Defibrillator 200 also includes a measurement circuit 220, as one ormore of its sensors or transducers. Measurement circuit 220 senses oneor more electrical physiological signals of the patient from sensor port219, if provided. Even if defibrillator 200 lacks sensor port 219,measurement circuit 220 may optionally obtain physiological signalsthrough nodes 214, 218 instead, when defibrillation electrodes 204, 208are attached to the patient. In these cases, the physiological inputreflects an ECG measurement. The patient parameter can be an ECG, whichcan be sensed as a voltage difference between electrodes 204, 208. Inaddition the patient parameter can be an impedance, which can be sensedbetween electrodes 204, 208 and/or the connections of sensor port 219.Sensing the impedance can be useful for detecting, among other things,whether these electrodes 204, 208 and/or sensing electrodes 209 are notmaking good electrical contact with the patient's body. These patientphysiological signals can be sensed, when available. Measurement circuit220 can then render or generate information about them as physiologicalinputs, data, other signals, etc. More strictly speaking, theinformation rendered by measurement circuit 220 is output from it, butthis information can be called an input because it is received by asubsequent device or functionality as an input.

Defibrillator 200 also includes a processor 230. Processor 230 may beimplemented in a number of ways. Such ways include, by way of exampleand not of limitation, digital and/or analog processors such asmicroprocessors and Digital Signal Processors (DSPs); controllers suchas microcontrollers; software running in a machine; programmablecircuits such as Field Programmable Gate Arrays (FPGAs),Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices(PLDs), Application Specific Integrated Circuits (ASICs), anycombination of one or more of these, and so on.

Processor 230 may include, or have access to, a non-transitory storagemedium, such as memory 238 that is described more fully later in thisdocument. Such a memory can have a non-volatile component for storage ofmachine-readable and machine-executable instructions. A set of suchinstructions can also be called a program. The instructions, which mayalso referred to as “software,” generally provide functionality byperforming methods as may be disclosed herein or understood by oneskilled in the art in view of the disclosed embodiments. In someembodiments, and as a matter of convention used herein, instances of thesoftware may be referred to as a “module” and by other similar terms.Generally, a module includes a set of the instructions so as to offer orfulfill a particular functionality. Embodiments of modules and thefunctionality delivered are not limited by the embodiments described inthis document.

Processor 230 can be considered to have a number of modules. One suchmodule can be a detection module 232. Detection module 232 can include aVentricular Fibrillation (VF) detector. The patient's sensed ECG frommeasurement circuit 220, which can be available as physiological inputs,data, or other signals, may be used by the VF detector to determinewhether the patient is experiencing VF. Detecting VF is useful, becauseVF typically results in SCA. Detection module 232 can also include aVentricular Tachycardia (VT) detector, and so on.

Another such module in processor 230 can be an advice module 234, whichgenerates advice for what to do. The advice can be based on outputs ofdetection module 232. There can be many types of advice according toembodiments. In some embodiments, the advice is a shock/no shockdetermination that processor 230 can make, for example via advice module234. The shock/no shock determination can be made by executing a storedShock Advisory Algorithm. A Shock Advisory Algorithm can make a shock/noshock determination from one or more ECG signals that are capturedaccording to embodiments, and determining whether a shock criterion ismet. The determination can be made from a rhythm analysis of thecaptured ECG signal or otherwise.

In some embodiments, when the determination is to shock, an electricalcharge is delivered to the patient. Delivering the electrical charge isalso known as discharging. Shocking can be for defibrillation, pacing,and so on.

Processor 230 can include additional modules, such as other module 236,for other functions. In addition, if internal monitoring device 281 isindeed provided, it may be operated in part by processor 230, etc.

Defibrillator 200 optionally further includes a memory 238, which canwork together with processor 230. Memory 238 may be implemented in anumber of ways. Such ways include, by way of example and not oflimitation, volatile memories, Nonvolatile Memories (NVM), Read-OnlyMemories (ROM), Random Access Memories (RAM), magnetic disk storagemedia, optical storage media, smart cards, flash memory devices, anycombination of these, and so on. Memory 238 is thus a non-transitorystorage medium. Memory 238, if provided, can include programs forprocessor 230, which processor 230 may be able to read and execute. Moreparticularly, the programs can include sets of instructions in the formof code, which processor 230 may be able to execute upon reading.Executing is performed by physical manipulations of physical quantities,and may result in functions, operations, processes, actions and/ormethods to be performed, and/or the processor to cause other devices orcomponents or blocks to perform such functions, operations, processes,actions and/or methods. The programs can be operational for the inherentneeds of processor 230, and can also include protocols and ways thatdecisions can be made by advice module 234. In addition, memory 238 canstore prompts for user 282, if this user is a local rescuer. Moreover,memory 238 can store data. This data can include patient data, systemdata and environmental data, for example as learned by internalmonitoring device 281 and outside monitoring device 180. The data can bestored in memory 238 before it is transmitted out of defibrillator 200,or stored there after it is received by defibrillator 200.

Defibrillator 200 may also include a power source 240. To enableportability of defibrillator 200, power source 240 typically includes abattery. Such a battery is typically implemented as a battery pack,which can be rechargeable or not. Sometimes a combination is used ofrechargeable and non-rechargeable battery packs. Other embodiments ofpower source 240 can include an AC power override, for where AC powerwill be available, an energy-storing capacitor, and so on. In someembodiments, power source 240 is controlled by processor 230.Appropriate components may be included to provide for charging orreplacing power source 240.

Defibrillator 200 may additionally include an energy storage module 250.Energy storage module 250 can be coupled to the support structure of theWCD system, for example either directly or via the electrodes and theirleads. Module 250 is where some electrical energy can be storedtemporarily in the form of an electrical charge, when preparing it fordischarge to administer a shock. In embodiments, module 250 can becharged from power source 240 to the desired amount of energy, ascontrolled by processor 230. In typical implementations, module 250includes a capacitor 252, which can be a single capacitor or a system ofcapacitors, and so on. In some embodiments, energy storage module 250includes a device that exhibits high power density, such as anultracapacitor. As described above, capacitor 252 can store the energyin the form of an electrical charge, for delivering to the patient.

Defibrillator 200 moreover includes a discharge circuit 255. When thedecision is to shock, processor 230 can be configured to controldischarge circuit 255 to discharge through the patient the electricalcharge stored in energy storage module 250. When so controlled, circuit255 can permit the energy stored in module 250 to be discharged to nodes214, 218, and from there also to defibrillation electrodes 204, 208, soas to cause a shock to be delivered to the patient. Circuit 255 caninclude one or more switches 257. Switches 257 can be made in a numberof ways, such as by an H-bridge, and so on. Circuit 255 can also becontrolled via user interface 280.

Defibrillator 200 can optionally include a communication module 290, forestablishing one or more wired or wireless communication links withother devices of other entities, such as a remote assistance center,Emergency Medical Services (EMS), and so on. The data can includepatient data, event information, therapy attempted, CPR performance,system data, environmental data, and so on. For example, communicationmodule 290 may transmit wirelessly, e.g. on a daily basis, heart rate,respiratory rate, and other vital signs data to a server accessible overthe internet, for instance as described in US 20140043149. This data canbe analyzed directly by the patient's physician and can also be analyzedautomatically by algorithms designed to detect a developing illness andthen notify medical personnel via text, email, phone, etc. Module 290may also include such interconnected sub-components as may be deemednecessary by a person skilled in the art, for example an antenna,portions of a processor, supporting electronics, outlet for a telephoneor a network cable, etc. This way, data, commands, etc. can becommunicated.

Defibrillator 200 can optionally include other components.

Operations according to embodiments is now described in more detail.FIG. 3A is a conceptual diagram for illustrating how electrodes of a WCDsystem may sense or capture ECG signals of the patient, and how thesesensed ECG signals may be used according to embodiments to yield a heartrate of the patient and other information. Two electrodes 304, 308 areattached to the torso of a patient, who is not shown. It will beappreciated that electrical noise may be introduced into the ECG signalat this point. Each of electrodes 304, 308 has a wire lead 305.Together, electrodes 304, 308 sense an ECG signal of the patient along asingle vector. Additional ECG signals may be sensed along additionalvectors.

FIG. 3A also shows a measurement circuit 320 and a processor 330, whichcan be made as described for measurement circuit 220 and processor 230.A filter 325 is optionally implemented in measurement circuit 320 and/orin processor 330. Filter 325 may be implemented as an analog filter, adigital filter, and so on. Filter 325 may help overcome some types ofECG noise by suppressing it, making this noise easier to detect, and soon. Processor 330 may further compute a heart rate 333 according toembodiments, as described in more detail further in this document.Computed heart rate 333 may be stored in memory 238. Heart rate 333 maythen be downloaded later from memory 238, transmitted wirelessly viacommunication module 290, displayed by a screen of user interface 280,and so on.

FIG. 3B is a conceptual diagram that includes a time axis 348. A sampleECG signal 319 of a patient is shown with reference to time axis 348.ECG signal 319 is intended to be drawn generically, and could appearhaving a waveform different from what is shown in FIG. 3B. It will berecognized that, in the instances where an ECG signal actually has theexact appearance seen in FIG. 3B, that ECG signal might indicate VT, oreven VF, but that is only for example.

ECG signal 319 has a first portion 317 and a second portion 318. Secondportion 318 has been sensed after sensing first portion 317. Such ECGsignal portions can be defined in a number of ways. For example, ECGportions 317, 318 can be a part of the sensed ECG signal that processor230 processes at one time. An ECG portion may be long enough to performa full ECG rhythm analysis. As such, An ECG portion may include severalQRS complexes. Or an ECG portion may be shorter. In addition, firstportion 317 includes noise events 374, examples of which are describedin more detail elsewhere in this document. And, while noise events 374are shown in FIG. 3B as definite events, occurring at specific times andhaving specific durations, etc., that is done only for purposes ofdiscussion. In real life, noise events in the ECG signal do not announcethemselves. Rather, embodiments of this disclosure detect when certaintypes of noise are within an ECG signal, react accordingly, and so on.

First ECG signal portion 317 may result in computing heart rate 333according to embodiments. Then a decision diamond 372 indicates that adecision may be made as to whether or not an analysis should beperformed. The analysis can be a full ECG analysis, or a confirmation ofthe heart rate computation, and so on. The answer for decision diamond372 may be provided by the value of heart rate 333, which was derivedfrom first signal portion 317. For example, a certain range of valuesfor heart rate 333 may give a NO answer, which is not indicated in FIG.3B. However, another range of values for heart rate 333 may give a YESanswer, which is also indicated in FIG. 3B with a check mark. If theanswer is YES, then according to an analysis operation 375, second ECGsignal portion 318 may be analyzed. As part of this analysis, second ECGportion 318 may be used to determine whether or not a shock criterion ismet, for example by advice module 234.

According to another decision diamond 370, another decision is indicatedas to whether or not a shock should be delivered. The answer fordecision diamond 370 may be provided by the result of analysis operation375. A NO answer is not indicated in FIG. 3B. Else, if the answer isYES, then according to a shock operation 311, a shock 111 isadministered to patient 82. For shock operation 311, processor 230 maycontrol, responsive to a shock criterion being met, discharge circuit255 to discharge through patient 82 an electrical charge that is storedin energy storage module 250, while support structure 170 is worn bypatient 82 so as to deliver a shock 111 to patient 82. Of course, beforeshock operation 311 another process may be undertaken where the patientis alerted by an alarm, challenged to demonstrate they are alive, and soon.

Operations 370 and 375 may be performed in a number of ways. Forinstance, the heart rate 333 may be computed again, for confirmation ofthe value arrived at in the first time. It may be computed in the sameway, or a different way, for example with additional safeguards, such asfor addressing noise. Plus, more parameters may be computed, such as aQRS width and so on.

Operations are now described where a WCD system reacts to high frequencyECG noise according to embodiments. These operations can be broadlydivided in situations where the ECG signal a) does not meet a shockcriterion, some of which are described in FIG. 4, and b) meets a shockcriterion, some of which are described in FIG. 5. These operations mayrefer to segments of the ECG signal including or not including highfrequency (H-F) noise events. The determination of whether such H-Fnoise events are included or not may be made depending on whether or nota High-Frequency (H-F) noise criterion is met, a segment noise criterionis met, and so on, more of which is described in more detail later inthis document.

FIG. 4 is a conceptual diagram that includes a time axis 448. A sampleECG signal 419 of a patient is shown with reference to time axis 448.ECG signal 419 is intended to be drawn generically, similarly with ECGsignal 319 of FIG. 3B. ECG signal 419 has a first portion 417 and asecond portion 418. Second portion 418 has been sensed after sensingfirst portion 417. A comment oval 496 contains the comment that it isnot known, at this time, whether or not first ECG portion 417 includesH-F noise.

In the example of FIG. 4, an analysis is made from first ECG signalportion 417. This analysis may be performed, for example, as describedfor decision diamond 370. From that analysis, it has been determinedthat a first shock criterion is not met. In other words, first ECGsignal portion 417 did not merit the WCD system administering a shock tothe patient. In FIG. 4, this determination is shown by a determinationpentagon 474, which includes the words “NO SHOCK”.

It should be noted that determination pentagon 474 was arrived atsubject to comment oval 496. However, since determination pentagon 474is “NO SHOCK” then, according to another comment oval 499, the WCDsystem does not care about comment oval 496. In other words, in thisinstance determination pentagon 474 stands as the WCD system'sdetermination, regardless of whether or not H-F noise events areincluded in ECG segments of first ECG portion 417. As such, sincedetermination pentagon 474 was “NO SHOCK”, any H-F noise in first ECGportion 417 is ignored.

The process may then continue with the second ECG portion 418, which issubsequent to first ECG portion 417, because it is sensed subsequentlyto it. Another determination pentagon 475 may be arrived at, and so on.

FIG. 5 is a conceptual diagram that includes a time axis 548. A sampleECG signal 519 of a patient is shown with reference to time axis 548.ECG signal 519 is intended to be drawn generically, similarly with ECGsignal 419 of FIG. 4. ECG signal 519 has a first portion 517 and asecond portion 518. Second portion 518 has been sensed after sensingfirst portion 517. A comment oval 596 contains the comment that it isnot known, at this time, whether or not first ECG portion 517 includesH-F noise.

In the example of FIG. 5, an analysis is made from first ECG signalportion 517. This analysis may be performed, for example, as describedfor decision diamond 370. From that analysis, it has been determinedthat a first shock criterion is indeed met. In other words, first ECGsignal portion 517 merits the WCD system administering a shock to thepatient. In FIG. 5, this determination is shown by a determinationpentagon 574, which includes the word “SHOCK”. In this situation,however, the possibility of H-F noise will not be ignored as it wasignored in FIG. 4.

Indeed, according to another decision diamond 530, it is determinedwhether or not first ECG portion 517 meets a High-Frequency (H-F) noisecriterion. Sample such criteria are described later in this document. Inthis example, the possible answers to decision diamond 530 are NO,denoted by an “X” and YES, denoted by a checkmark. If the answer is NOthen, according to an operation 511 a shock is administered to thepatient, similarly with operation 311.

If the answer to decision diamond 530 is yes, then a comment oval 597indicates that comment oval 596 is determined to have been H-F noise.According to a related operation 570, it can be determined from secondportion 518 of the sensed ECG signal, whether or not a shock criterionis met. This operation 570 may be performed, for example, as describedfor decision diamond 370. The determination that is arrived at this wayis either determination pentagon 575 (“NO SHOCK”), or determinationpentagon 577 (“SHOCK”). Determination pentagon 575 (“NO SHOCK”) isassociated with comment oval 598, which indicates that determinationpentagon 574 (“SHOCK”) was false, and probably arrived at due to H-Fnoise. On the other hand, determination pentagon 577 (“SHOCK”) can befollowed by an operation 515 similar to operation 511, where a shock isadministered to the patient, and so on.

The devices and/or systems mentioned in this document perform functions,processes and/or methods. These functions, processes and/or methods maybe implemented by one or more devices that include logic circuitry. Sucha device can be alternately called a computer, and so on. It may be astandalone device or computer, such as a general purpose computer, orpart of a device that has one or more additional functions. The logiccircuitry may include a processor and non-transitory computer-readablestorage media, such as memories, of the type described elsewhere in thisdocument. Often, for the sake of convenience only, it is preferred toimplement and describe a program as various interconnected distinctsoftware modules or features. These, along with data are individuallyand also collectively known as software. In some instances, software iscombined with hardware, in a mix called firmware.

Moreover, methods and algorithms are described below. These methods andalgorithms are not necessarily inherently associated with any particularlogic device or other apparatus. Rather, they are advantageouslyimplemented by programs for use by a computing machine, such as ageneral-purpose computer, a special purpose computer, a microprocessor,a processor such as described elsewhere in this document, and so on.

This detailed description includes flowcharts, display images,algorithms, and symbolic representations of program operations within atleast one computer readable medium. An economy is achieved in that asingle set of flowcharts is used to describe both programs, and alsomethods. So, while flowcharts described methods in terms of boxes, theyalso concurrently describe programs.

Methods are now described.

FIG. 6 shows a flowchart 600 for describing methods according toembodiments. Flowchart 600 includes operations that are linked byarrows. In addition, flowchart 600 is annotated with determinationpentagons repeated from FIG. 4 and FIG. 5 where applicable.

According to an operation 610, a portion is sensed of an ECG signal ofthe patient. Such portions can be sensed sequentially, for example asseen above with ECG signal portions pairs 317 & 318, 417 & 418 and 517 &518.

A subsequent operation 671 is also a decision diamond 671. According tooperation 671, it can be determined whether or not a first shockcriterion is met. The determination can be made from the signal portionsensed at operation 610. The shock criterion can be the same as that ofdecision diamond 370, or different. If, at decision diamond 671 theanswer is NO, then that is equivalent to determination pentagon 474 ofFIG. 4, and execution may return to another operation, such as operation610.

If, at decision diamond 671 the answer is YES, then that is equivalentto determination pentagon 574 of FIG. 5. Then execution may proceed toanother operation 630, which is also a decision diamond 630. Accordingto operation 630, it can be determined whether or not the first portionof the sensed ECG signal, which met the first shock criterion ofoperation 671, also meets a High-Frequency (H-F) noise criterion.Examples of such noise criteria are described later in this document.

If, at decision diamond 630 the answer is NO, then execution may proceedto another operation 611 and shock the patient, similarly with operation511. After that, execution may return to another operation, such asoperation 610.

If, at decision diamond 630 the answer is YES, then execution mayproceed to another operation 650 where a next, or second, portion of theECG signal can be sensed. In other words, operation 650 is similar tooperation 610.

Execution may then proceed to operation 672, which is also a decisiondiamond 672. According to operation 672, it may be determined, from thesecond portion of the sensed ECG signal, whether or not a second shockcriterion is met. The second shock criterion can be the same ordifferent as the first shock criterion. This second portion of the ECGsignal can be sensed and analyzed for purposes of confirmation of theYES answer at decision diamond 671.

If, at decision diamond 672 the answer is NO, then that is equivalent todetermination pentagon 575 of FIG. 4, and execution may return toanother operation, such as operation 610.

If, at decision diamond 672 the answer is YES, then that is equivalentto determination pentagon 577 of FIG. 5. Then execution may proceed tooperation 611, and the patient is shocked, as above. It will beunderstood, however, that the path to operation 611 via a YES answer atdecision diamond 630, and then operations 650 and 672 may take longerthan the path through a NO answer at decision diamond 630. As such, theshock of operation 611 maybe delivered at least 5 seconds later than theshock that would have been delivered responsive to the H-F noisecriterion not being met at operation 630.

Noise criteria according to embodiments are now described in moredetail. In some embodiments, a potential R peak of a QRS complex isidentified in a first portion of the sensed ECG signal. Then an ECGsegment becomes defined as a segment of the ECG signal that correspondsto the potential R peak. It is preferred that the ECG segment becomesdefined in proximity with the potential R peak, and in fact maybe eveninclude the potential R peak that it corresponds to. Then the H-F noisecriterion can be met responsive to the ECG segment meeting a segmentnoise criterion. Examples are now described.

FIG. 7 shows an ECG signal of patient 82 in a time diagram 709. Diagram709 has an ECG amplitude axis 707 and a time axis 708. The shown ECGsignal is somewhat-idealized, noise-free, and includes three fullheartbeats. In particular, the ECG signal includes three QRS complexes,each of which is followed by a T-wave of lesser amplitude. These QRScomplexes include three R peaks 721, 722, 723. The ECG signal hoversaround a horizontal baseline value BL. Baseline value BL can beconsidered to be zero, but in real life it might be changing value,possibly due to noise. In this somewhat-idealized ECG signal, a P-wavebefore the QRS complex and a U-wave after the QRS complex are not shownat all.

Even though the ECG signal of diagram 709 is somewhat-idealized, itserves as a good basis for describing embodiments, as if it were the ECGsignal that was sensed. For example, R peaks 721, 722, 723 can bedetected in an ECG signal of patient 82, even if that signal containsnoise. These R peaks 721, 722, 723 can be used for detecting thepatient's heart rate 333, because their large amplitude relative to theremainder of the ECG signal makes them more easy to identify and/ordetect. In particular, in diagram 709, three ECG segments are definedaccording to embodiments, as segments of ECG signal portion that includeR peaks 721, 722, 723 respectively.

FIG. 7 shows ECG segments more explicitly in another time diagram 759.Diagram 759 has an ECG Segment Amplitude axis 757 and a time axis 758.ECG segments 751, 752, 753 are segments of the ECG signal of diagram 709that are within respective time windows 791, 792, 793. As such, ECGsegments 751, 752, 753 have the same duration as the duration of timewindows 791, 792, 793.

An ECG segment according to embodiments can be defined to have aduration that isolates the potential R peak from other features. Forexample, an ECG segment can have a duration between 160 ms and 200 ms,such as 180 milliseconds. In FIG. 7, that duration is shown as the widthof time windows 791, 792, 793.

An ECG segment according to embodiments can be defined to correspond toan R peak of an ECG signal as a segment of the ECG signal that includesthe R peak. In some embodiments, the ECG segment starts at the potentialR peak, as in the example of FIG. 7. In other embodiments, the ECGsegment starts before the potential R peak and ends after it. Forexample, the potential R peak can be at the center of the ECG segment.As seen later in this document, a segment can be used to analyze thevalidity of a potential R peak.

It will be understood that R peaks 721, 722, 723 can be identified aspotential R peaks, if the ECG signal of diagram 709 is the sensed ECGsignal. In that case the ECG segments 751, 752, 753 can be defined toinclude potential R peaks 721, 722, 723.

FIG. 7 also shows a time axis 748 that indicates only the timeoccurrences 741, 742, 743 of R peaks 721, 722, 723, respectively.Moreover, these R peaks 721, 722, 723 can be considered in pairs ofsuccessive R peaks, to define time intervals. In particular, the pair ofpeaks 721 and 722 defines a time interval 701 from time occurrences 741,742, while the pair of peaks 722 and 723 defines a time interval 702from time occurrences 742, 743. Time intervals 701, 702 are sometimescalled R-R intervals of the ECG signal. The durations of time intervals701, 702 can be measured, and heart rate 333 of the patient can be thuscomputed from them.

It will be recognized that this process of computing heart rate 333 frompeaks 721, 722, 723 in the ECG signal is the same regardless of howthese peaks 721, 722, 723 are detected. Medical devices sometimesmeasure the ECG signal electronically and focus on these peaks to detectthe R-R interval, for example as per the above. Other times, peaks 721,722, 723 correspond with peaks in the patient's blood pressure, whichcan be sensed by a person placing their hand against the neck or a wristof a patient.

It can be more difficult, however, to measure the patient's heart ratefrom these peaks in the presence of noise in the ECG signal. An exampleis are now described.

FIG. 8 shows a time diagram 809. Diagram 809 has an R peaks axis 807 anda time axis 808. Diagram 809 depicts only R peaks 821, 822, 823, 824 ofa patient's ECG signal portion, with all other values of the ECG signalbeing shown as zero for simplification. This simplification isacceptable in this instance, as FIG. 8 is used for discussing ECGsegments as per the above, where large peaks are being detected.

FIG. 8 also shows a time diagram 839 to depict sample noise that couldbe added to the ECG of diagram 829. Diagram 839 has a Large Noise Peaksaxis 837 and a time axis 838. Diagram 839 depicts only one large noisepeak 833, with all other values being shown as zero for simplification,since large peaks are being detected. It will be recognized that noisepeak 833 is an example of a noise event 374.

FIG. 8 also shows a time diagram 829. Diagram 829 has a Potential RPeaks axis 827 and a time axis 828. Time diagram 829 depicts thesuspected or potential R peaks of a sample sensed ECG signal portion.Time diagram 829 in this example is arrived at as a sum of time diagrams809 and 839.

According to embodiments, therefore, there are five potential R peaks821, 822, 823, 833, 824 in time diagram 829. Given the arrangement ofthe drawings above, the reader can tell that, of these potential R peaks821, 822, 823, 833, 824, one of them (833) is false due to noise, whilethe other ones are true. As such, large noise peak 833 represents afalse detection of a QRS complex. This threatens the accuracy of thecalculation of heart rate 333, as will be understood from the interceptsin time axis 748 of FIG. 7; indeed, more such time intercepts mayfalsely indicate that the patient is having tachycardia or worse.

In embodiments, this risk is addressed by defining ECG segments 851,852, 853, 854, 855 as segments of ECG signal portion in time diagram 809that include the identified potential R peaks 821, 822, 823, 833, 824respectively. Such may be implemented by first defining time windows891, 892, 893, 894, 895 starting from these identified potential R peaks821, 822, 823, 833, 824.

FIG. 8 shows ECG segments 851, 852, 853, 854, 855 more explicitly inanother time diagram 859. Diagram 859 has an ECG Segment Amplitude axis857 and a time axis 858. ECG segments 851, 852, 853, 854, 855 aresegments of the ECG signal of diagram 829 that are within respectivetime windows 891, 892, 893, 894, 895. As such, ECG segments 851, 852,853, 854, 855 have the same duration as the duration of time windows891, 892, 893, 894, 895.

In embodiments, ECG segments 851, 852, 853, 854, 855 can be used todetect which of these potential R peaks is noise. In some embodiments,the H-F noise criterion may be met responsive to the ECG segment meetinga segment noise criterion.

In the sample embodiments that are described below, the ECG signalportion and/or the ECG segment may be first filtered, for example byfilter 325. For instance, filter 325 may be a filter passing frequenciesbetween 8 Hz and 25 Hz. In such embodiments, the H-F noise criterion ismet responsive to the filtered ECG segment meeting the segment noisecriterion.

Two examples of segment noise criteria are now described.

FIG. 9 shows a time diagram 959. Diagram 959 has an ECG segmentamplitude axis 957 and a time axis 958. Diagram 959 depicts two sampleECG segments 953, 954, which have been defined by respective timewindows 993, 994. In turn, time windows 993, 994 correspond to potentialR peaks of a sensed ECG signal portion, and maybe even include these Rpeaks.

In FIG. 9, ECG segments 953, 954 are shown as approximately sinusoidalwaveforms, but that is only by way of example. For instance, thesewaveforms are rounded where they have local maxima and local minima, butthey could have edges there instead of being rounded, such as ECG signal319. In fact, in embodiments where the ECG segment includes a suspectedor potential R peak of a QRS complex, one of the edges is sharp and itspulse can have much higher amplitude than its neighboring pulses. Thesewaveforms being rounded, however, is adequate for this particularexplanation.

According to decision diamonds 933, 934, ECG segments 953, 954 aresubjected to determinations of whether or not a segment noise criterionis met. In some embodiments, the criteria of decision diamonds 933, 934are the same, while in others different. In some embodiments, an ECGsegment is subjected to more than one segment noise criterion, and soon.

In this example, the segment noise criterion is met responsive to theECG segment containing more zero-crossings than a crossings threshold.The crossings threshold can be advantageously determined by the chosenduration of time windows 993, 994, and given a target density orfrequency of zero crossings.

In this example the crossings threshold is five. ECG segment 953 hasfour zero crossings 963, which are not more than the threshold of five.As such, the segment noise criterion is not met, and the answer todecision diamond 933 is NO. On the other hand, ECG segment 954 has sixzero crossings 964, which are more than the threshold of five. As such,the segment noise criterion is met, and the answer to decision diamond934 is YES.

FIG. 9 also shows a time diagram 989. Diagram 989 has an ECG segmentamplitude axis 987 and a time axis 988. Diagram 989 depicts the ECGsegments of diagram 959 that survive the segment noise criterion ofdecision diamonds 933, 934. As such, ECG segment 953 survives, while ECGsegment 954 is discarded. Accordingly, the R peak that gave rise tosegment 954 can be discarded as being due to H-F noise, and a moreaccurate result can be reached by the algorithm of the WCD system.

FIG. 10 shows a time diagram 1059. Diagram 1059 has an ECG segmentamplitude axis 1057 and a time axis 1058. Diagram 1059 depicts twosample ECG segments 1053, 1054, which have been defined by respectivetime windows 1093, 1094 that are near potential R peaks of an ECG signalportion. In turn, time windows 1093, 1094 correspond to potential Rpeaks of a sensed ECG signal portion, and maybe even include these Rpeaks.

In FIG. 10, ECG segments 1053, 1054 are shown as approximatelysinusoidal waveforms, but that is only by way of example. For instance,these waveforms could have edges instead of being rounded at their localmaxima and local minima. In fact, in embodiments where the ECG segmentincludes a suspected or potential R peak of a QRS complex, one of theedges is sharp and its pulse can have much higher amplitude than itsneighboring pulses. These waveforms being rounded is adequate for thisparticular explanation.

According to decision diamonds 1033, 1034, ECG segments 1053, 1054 aresubjected to determinations of whether or not a segment noise criterionis met. In this example, the segment noise criterion is met responsiveto the ECG segment containing at least one peak briefer than a thresholdduration. In some embodiments, the threshold duration is 25 milliseconds(ms).

In this example the threshold duration is shown as a time window 1099.ECG segment 1053 has no pulse more brief or shorter than time window1099. As such, the segment noise criterion is not met, and the answer todecision diamond 1033 is NO. On the other hand, ECG segment 1054 has atleast one pulse more brief than time window 1099, for instance asevidenced by zero crossing 1064. As such, the segment noise criterion ismet, and the answer to decision diamond 1034 is YES.

FIG. 10 also shows a time diagram 1089. Diagram 1089 has an ECG segmentamplitude axis 1087 and a time axis 1088. Diagram 1089 depicts the ECGsegments of diagram 1059 that survive the segment noise criterion ofdecision diamonds 1033, 1034. As such, ECG segment 1053 survives, whileECG segment 1054 is discarded. Accordingly, the R peak that gave rise tosegment 1054 can be discarded as being due to H-F noise, and a moreaccurate result can be reached by the algorithm of the WCD system.

In other embodiments a noisiness ratio can be used for ECG portion 517.The noisiness ratio can be defined from a number of segments withinportion 517 that meet the segment noise criterion over the total numberof potential R peaks within portion 517. In such embodiments, the H-Fnoise criterion can be met instead responsive to the noisiness ratioexceeding a threshold.

In the methods described above, each operation can be performed as anaffirmative act or operation of doing, or causing to happen, what iswritten that can take place. Such doing or causing to happen can be bythe whole system or device, or just one or more components of it. Itwill be recognized that the methods and the operations may beimplemented in a number of ways, including using systems, devices andimplementations described above. In addition, the order of operations isnot constrained to what is shown, and different orders may be possibleaccording to different embodiments. Examples of such alternate orderingsmay include overlapping, interleaved, interrupted, reordered,incremental, preparatory, supplemental, simultaneous, reverse, or othervariant orderings, unless context dictates otherwise. Moreover, incertain embodiments, new operations may be added, or individualoperations may be modified or deleted. The added operations can be, forexample, from what is mentioned while primarily describing a differentsystem, apparatus, device or method.

A person skilled in the art will be able to practice the presentinvention in view of this description, which is to be taken as a whole.Details have been included to provide a thorough understanding. In otherinstances, well-known aspects have not been described, in order to notobscure unnecessarily this description.

Some technologies or techniques described in this document may be known.Even then, however, it does not necessarily follow that it is known toapply such technologies or techniques as described in this document, orfor the purposes described in this document.

This description includes one or more examples, but this fact does notlimit how the invention may be practiced. Indeed, examples, instances,versions or embodiments of the invention may be practiced according towhat is described, or yet differently, and also in conjunction withother present or future technologies. Other such embodiments includecombinations and sub-combinations of features described herein,including for example, embodiments that are equivalent to the following:providing or applying a feature in a different order than in a describedembodiment; extracting an individual feature from one embodiment andinserting such feature into another embodiment; removing one or morefeatures from an embodiment; or both removing a feature from anembodiment and adding a feature extracted from another embodiment, whileproviding the features incorporated in such combinations andsub-combinations.

In general, the present disclosure reflects preferred embodiments of theinvention. The attentive reader will note, however, that some aspects ofthe disclosed embodiments extend beyond the scope of the claims. To therespect that the disclosed embodiments indeed extend beyond the scope ofthe claims, the disclosed embodiments are to be considered supplementarybackground information and do not constitute definitions of the claimedinvention.

In this document, the phrases “constructed to” and/or “configured to”denote one or more actual states of construction and/or configurationthat is fundamentally tied to physical characteristics of the element orfeature preceding these phrases and, as such, reach well beyond merelydescribing an intended use. Any such elements or features can beimplemented in a number of ways, as will be apparent to a person skilledin the art after reviewing the present disclosure, beyond any examplesshown in this document.

Any and all parent, grandparent, great-grandparent, etc. patentapplications, whether mentioned in this document or in an ApplicationData Sheet (“ADS”) of this patent application, are hereby incorporatedby reference herein as originally disclosed, including any priorityclaims made in those applications and any material incorporated byreference, to the extent such subject matter is not inconsistentherewith.

In this description a single reference numeral may be used consistentlyto denote a single item, aspect, component, or process. Moreover, afurther effort may have been made in the drafting of this description touse similar though not identical reference numerals to denote otherversions or embodiments of an item, aspect, component or process thatare identical or at least similar or related. Where made, such a furthereffort was not required, but was nevertheless made gratuitously so as toaccelerate comprehension by the reader. Even where made in thisdocument, such a further effort might not have been made completelyconsistently for all of the versions or embodiments that are madepossible by this description. Accordingly, the description controls indefining an item, aspect, component or process, rather than itsreference numeral. Any similarity in reference numerals may be used toinfer a similarity in the text, but not to confuse aspects where thetext or other context indicates otherwise.

The claims of this document define certain combinations andsubcombinations of elements, features and acts or operations, which areregarded as novel and non-obvious. Additional claims for other suchcombinations and subcombinations may be presented in this or a relateddocument. These claims are intended to encompass within their scope allchanges and modifications that are within the true spirit and scope ofthe subject matter described herein. The terms used herein, including inthe claims, are generally intended as “open” terms. For example, theterm “including” should be interpreted as “including but not limitedto,” the term “having” should be interpreted as “having at least,” etc.If a specific number is ascribed to a claim recitation, this number is aminimum but not a maximum unless stated otherwise. For example, where aclaim recites “a” component or “an” item, it means that it can have oneor more of this component or item.

In construing the claims of this document, the inventor(s) invoke 35U.S.C. § 112(f) only when the words “means for” or “steps for” areexpressly used in the claims. Accordingly, if these words are not usedin a claim, then that claim is not intended to be construed by theinventor(s) in accordance with 35 U.S.C. § 112(f).

What is claimed is:
 1. A wearable cardioverter defibrillator (WCD)system, comprising: a support structure configured to be worn by anambulatory patient; an energy storage module configured to store anelectrical charge; a discharge circuit coupled to the energy storagemodule; electrodes configured to sense an Electrocardiogram (ECG) signalof the patient; an a processor configured to: determine from a firstportion of the sensed ECG signal, whether a first shock criterion ismet, determine whether the first portion of the sensed ECG signal meetsa High-Frequency (H-F) noise criterion, wherein H-F noise is present inthe sensed EGC signal when a peak in the sensed ECG signal has aduration 25 milliseconds or less, responsive to the first shockcriterion being met and the H-F noise criterion not being met, controlthe discharge circuit to discharge the stored electrical charge throughthe patient while the support structure is worn by the patient so as todeliver a shock to the patient, else responsive to the first shockcriterion being met and the H-F noise criterion being met, determinefrom a second portion of the sensed ECG signal, whether a second shockcriterion is met, the second portion sensed subsequently to the firstportion and, responsive to the second shock criterion being met, controlthe discharge circuit to discharge the stored electrical charge throughthe patient while the support structure is worn by the patient todeliver a shock to the patient; wherein the processor is furtherconfigured to: identify a potential R peak of a QRS complex in the firstportion of the sensed ECG signal, define an ECG segment as a segment ofthe first ECG signal portion that corresponds to the potential R peak,and determine whether the H-F noise criterion is met responsive to theECG segment meeting a segment noise criterion, the segment noisecriterion being met responsive to the ECG segment containing at leastone peak briefer than a threshold duration of 25 ms.
 2. The WCD systemof claim 1, in which the second shock criterion is the same as the firstshock criterion.
 3. The WCD system of claim 1, in which the ECG segmentincludes the potential R peak that it corresponds to.
 4. The WCD systemof claim 1, in which the ECG segment starts at the potential R peak thatit corresponds to.
 5. The WCD system of claim 1, in which the ECGsegment has a duration between 160 ms and 200 ms.
 6. The WCD system ofclaim 1, further comprising: a filter to filter the ECG segment, andwherein the processor is further configured to: determine whether theH-F noise criterion is met responsive to the filtered ECG segmentmeeting the segment noise criterion.
 7. The WCD system of claim 6, inwhich the filter is configured to pass frequencies between 8 Hz and 25Hz.
 8. The WCD system of claim 6, in which the ECG segment has aduration between 160 ms and 200 ms.
 9. The WCD system of claim 6, inwhich the ECG segment starts at the potential R peak that it correspondsto.
 10. The WCD system of claim 1, in which the segment noise criterionis met responsive to the ECG segment containing more zero-crossings thana crossings threshold.
 11. The WCD system of claim 10, in which thecrossings threshold is five.
 12. The WCD system of claim 10, in whichthe ECG segment has a duration between 160 ms and 200 ms.
 13. The WCDsystem of claim 1, in which the ECG segment has a duration between 160ms and 200 ms.